Dual-mode surface-enhanced Raman scattering sensors assembled from graphene plasmonic nanoresonator on photoactive SOI

Surface-enhanced Raman scattering (SERS) has been explored and acts as a practical analytical detection approach. However, constructing highly sensitive SERS substrates usually involves expensive materials and tedious preparation processes, and SERS substrates often cannot be reused. Herein, direct hetero-integration of three-dimensional graphene (3D-graphene) with silicon-on-insulator (SOI) substrate can be utilized as a highly stable, ultra-sensitive, low cost and reusable SERS substrates through plasma-assisted chemical vapor deposition (PACVD). The novel nanocavity construction of the 3D-graphene combines with the optical cavity system of the SOI to improve the interaction between the incident light and 3D-graphene, which is a model for doubly-reinforced Raman scattering. These properties enhance electronic interactions between 3D-graphene, target molecules, and SOI substrates, thereon improving chemical/charge transfer effects in heterojunctions. The as-designed 3D-graphene/SOI heterojunction has detection limits of ∼10⁻¹⁰ M for rhodamine B (RB) and rhodamine 6G (R6G), and the detection limit for crystalline violet (CRV) is ∼10⁻⁸ M, which is better than the existing reported graphene-based SERS. Our study confirms the efficient carrier transfer mechanism in the 3D-graphene/SOI heterojunction and enhances the chemical/charge transfer mechanism of SERS by double-enhanced high-light absorption. In addition, erythrosine B (EB) and carmine, considered harmful pigment additives in fruit-flavored beverages, were selected as the detection targets with a detection limit of about 10⁻⁹ M and 10⁻⁸ M, suggesting that 3D-graphene/SOI heterojunction-based SERS can be applied in the food safety field.